# How to find the velocity of the protons and antiprotons?

1. Apr 28, 2012

### yy205001

1. The problem statement, all variables and given/known data

Some particle accelerators allow protons (p+) and antiprotons (p-) to circulate at equal speeds in opposite directions in a device called a storage ring. The particle beams cross each other at various points to cause p+ + p- collisions. In one collision, the outcome is p+ + p- yields e+ + e- + γ + γ, where γ represents a high energy gamma-ray photon. The electron and position are ejected from the collision at 0.9999995c and the gamma-ray photon wavelengths are found to be 1.0 X 10-6 nm. What were the proton and antiproton speeds prior to the collision?

m(e-)=9.11e-31(kg), λ(γ)=1e-6(nm)

2. Relevant equations
Ei = Ef
E=mc^2 - 0.5mu^2
E=γmc^2

3. The attempt at a solution

2. Apr 28, 2012

### tiny-tim

hi yy205001!

(try using the X2 button just above the Reply box )

conservation of energy?

3. Apr 28, 2012

### yy205001

i dont know what does'' p+ + p- yields e+ + e- + γ + γ'' tell me?

4. Apr 29, 2012

### tiny-tim

well, you know the mass of everything, and you know the wavelength of the photons, and the speed of the electrons

5. Apr 30, 2012

### yy205001

but how can we get the mass of the gamma ray?

6. Apr 30, 2012

### tiny-tim

the gamma ray is a photon, with zero mass

7. May 1, 2012

### yy205001

oh!! thank you=]